The invention relates to a nozzle, preferably for use in sprinklers and spray heads, for spraying medium, the nozzle comprising a housing, an inlet end and a first conduit leading from the inlet end to a nozzle opening to enable the spraying of the medium through the nozzle.
The invention also relates to a fire fighting installation comprising a number of sprinklers or spray heads, including nozzles, each nozzle comprising a housing, an inlet end and a first conduit leading from the inlet end to a nozzle opening for spraying medium through the nozzle, the sprinklers or spray heads being arranged to be activated depending on the location of the fire so that only some of the sprinklers or spray heads are activated at the beginning of the extinguishing process; and the installation also comprising a pressure source and lines for supplying the extinguishing medium to the sprinklers or spray heads.
The invention also relates to a fire fighting installation comprising a number of sprinklers or spray heads, including nozzles, each nozzle comprising a housing, an inlet end and a first conduit leading from the inlet end to a nozzle opening for spraying medium through the nozzle, the sprinklers and spray heads being arranged to be activated depending on the location of the fire so that only some of the sprinklers or spray heads are activated at the beginning of the extinguishing process; and the installation also comprising a pressure source comprising a pressure accumulator, and lines for supplying the extinguishing medium to the sprinklers or spray heads.
The flow of the medium, such as liquid, outlet from the nozzle is dependent on the pressure p which discharge the medium through the nozzle.
The dependence is such that the quantity Q of flow fulfils the formula Q=Kp, where K is the resistance of the nozzle. The K value depends on the diameter d of the nozzle opening in accordance with the formula K=0.78 d.sup.2, when the opening is a so-called short opening. From the above formulae it is apparent that the flow will not increase much when the pressure rises and the K value is constant. In some applications, for example in fire fighting, a great increase in the flow is desirable when the pressure rises, as will be understood from the following.
The fire fighting systems are usually designed to cover a defined area or large space. On the land base applications the basis of design is an area of 205 m.sup.2, which requires 15 sprinklers. The drive or pressure units of the fire fighting systems are designed in accordance with the area or space so that a desired pressure and flow of water are achieved for the area to be covered. In the case of a sprinkler system in which the sprinklers and/or spray heads are activated by heat either individually or in groups, the fire can usually be brought under control even with only a few of the spray heads or sprinklers necessitated by the design. The controlling of the fire means that it cannot spread. The fire can usually be brought under control with two sprinklers, whereby it is not necessary for any more sprinklers to be activated. Even when the fire is under control, however, it continues to burn and produce a notable amount of smoke and gas. The flue gases can be very toxic and even kill people; in addition, the smoke hampers the visibility and thereby hinders the firemen in their work. In situations like this, only a fraction of the fire fighting power of the drive or pressure units of the fire extinguishing systems are used, which can be shown by calculations. The power P used is directly proportional to the flow Q and pressure p and inversely proportional to the efficiency of the drive unit.
The pressure unit of the fire fighting installation is designed so that a predefined flow of water with a predefined pressure is achieved in the area to be covered. If, for example, the area requires 15 sprinklers and the flow of a sprinkler is 13 l/min at a pressure of 60 bar, the total flow of the fire fighting installation is 195 l/min when all the sprinklers have been activated. When the loss of pressure in the lines is 20 bar and the efficiency is 0.85, the power demand in the pressure unit is 30 kW. If only two sprinklers are activated, only 13% of the power is used, i.e. about 4 kW. The K value of the nozzle is here 1.7, and the efficiency is 60%.
The drawback in the previously known fire fighting installations is that only part of the power of the pressure unit is used for extinguishing the fire when only some of the nozzles of the fire fighting installation are activated. Consequently, the fire cannot often be extinguished immediately. In order that the fire could always be extinguished as quickly as possible, very expensive systems would have to be used.